INORGANIC CHEMISTRY
▸ Molecule boasts four group 15 elements One of the joys of inorganic chemistry is exploring the periodic table to see what new and interesting things can be done with the elements. For Alexander Hinz of Oxford University and Axel Schulz and Alexander Villinger of the University of Rostock, that joy comes from stringing together as many different elements in a periodic group as possible to form heterocyclic rings. The team was working toward making a ring containing four different pnictogens (group 15
Cl Cl Sb N
As
P
CREDIT: ANAL. CHEM. (MICROGRAPH); ANDY BAKER/U OF NEW SOUTH WALES (CAVE)
Four-element pnictogen chain compound elements, N to Bi), but they were unable to close the linear precursor. So the researchers have settled for now on reporting the acyclic compound, which includes an unprecedented Sb–N–As=P chain (Chem. Eur. J. 2016, DOI: 10.1002/chem.201601916). “To the best of our knowledge, our compound is the first acyclic molecular species featuring four different pnictogens in a chain,” Schulz tells C&EN. “In principle, it should also be possible to include bismuth, but that would be much more difficult.” On the periodic table, only groups 13 to 15 are likely to pull off the complete feat. So far, there are no examples from group 13 (B to Tl) with four or more elements. And although there are a few molecules containing various combinations of four group 14 elements (C to Pb), there is no species with all five.—STEVE RITTER
GEOCHEMISTRY
▸ Cave drip water may contain fire evidence
MICROFLUIDICS
Device grows microbes single file When a bacterium multiplies on a surface, its offspring typically stay close. They pile up in mounds, making it difficult to study individual cells. Researchers have now built a transparent array of nanochannels where microbes grow single file so they can study a bacterium and its daughter cells over multiple generations (Anal. Chem. 2016, DOI: 10.1021/acs.analchem.6b00889). Tracking single cells in this way could help identify how microbes acquire traits such as antibiotic resistance. Stephen C. Jacobson and colleagues at Indiana University, Bloomington, fabricated a ladder-shaped pattern in a polymer film on a glass slide and covered it with another glass layer. Microchannels for supplying nutrient medium formed the ladder’s side rails, and nanochannels several hundred nanometers wide—matching the width of the bacteria—formed the rungs. The team first confirmed that Bacillus subtilis bacteria grew at the same rate in the device as in standard culture. Cells grow single file Next, they engineered a B. subtilis strain to carry within nanochannels a green fluorescence gene controlled by a genetic built on a microscope element known to be activated in only a fraction slide. Microchannels of cells in a population. Over five generations, along the sides supply the team tracked which cells glowed and which nutrient medium. didn’t. Daughter cells were more likely to glow if their parent did, but the correlation declined with every generation.— JYOTI
MADHUSOODANAN, special to C&EN
University of New South Wales measured 18O/16O ratios in drip water at two sites in Yonderup Cave beneath a forest in southwestern Australia. Because 18O is heavier than 16O, it evaporates more slowly, and its enrichment in water, therefore, can be a marker for changing temperatures. But the authors found that the drip water at one site in Yonderup Cave was highly enriched in 18O compared with ratios predicted by models.
In addition, oxygen isotope ratios at nearby Golgotha Cave showed no such enrichment, even though both caves are in the same arid environment. However, an intense wildfire in 2005 led to the loss of a giant tree directly over the 18O-enriched area in Yonderup Cave. The increased evaporation could explain the isotope findings. The authors say such isotopic changes could persist for five to 10 years.—ELIZABETH WILSON
Drip water in Yonderup Cave contains evidence of an aboveground fire.
Water that drips from aboveground into caves to form stalactites and stalagmites carries with it paleoclimate signatures in isotopic ratios. Now, researchers say this geochemical record may be altered by fires, which could add complexity to paleoclimate interpretations (Hydrol. Earth Syst. Sci. 2016, DOI: 10.5194/hess-20-2745-2016). From 2005 to 2011, a team led by Andy Baker, Gurinder Nagra, and Pauline C. Treble of the JULY 25, 2016 | CEN.ACS.ORG | C&EN
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